Recovering roofs - Kent Local Authority Building Control

Recovering roofs

We are receiving more and more reports about builders and roofing contractors who have recovered roofs but have not involved Building Control. In the majority of cases we found that the reason was that contractors were not aware of how the changes in the Building Regulations affected their work.

There are two ways you can gain Building Regulation approval. The first way is for your roofer to be registered with The National Federation of Roofing Contractors (NFRC) under their scheme called CompetentRoofer, which is part of the Government's Competent Persons Scheme. This enables the roofer to self-certify that the roofing work meets the requirements of the regulations. The notification of compliance using this route must be notified to your local authority building control office within 30 days of completion of the works. If the roofer is not registered with the scheme, the alternative way to gain approval is to apply to your local authority building control office for approval.

If you choose to use your local authority building control office to gain approval, the following background and advice should assist you in achieving compliance with the requirements.

Competent Roofer approval scheme

How the Building Regulations have changed

The Building Regulations changed on 5 April 2006. Before that date you would only have needed to apply for Building Regulations approval if you were changing the type of roof covering, for example, changing from slates to concrete tiles.

Now you need to apply even if the new roof covering is a like for like replacement. The reason for this is that the Government has decided that it is a good opportunity to increase the thermal insulation of a building, so that fuel and power are conserved. The requirement applies to both pitched and flat roofs.

The Building Regulations however only ask for the thermal performance to be upgraded to the required levels where it is reasonable to do so. The regulations define 'reasonable' using three tests:

  • Is increasing thermal performance technically feasible? In most cases there is a technically feasible solution.
  • Is increasing thermal performance functionally feasible? In most cases there is a functionally feasible solution but care must be taken not to increase the chances of the condensation occurring in a roof. This is a particular concern for lead roofs where the insulation is directly under the lead, (i.e. warm deck roofs).
  • Is increasing the thermal performance economically feasible? Most re-roofing projects will be economically viable although for flat roofs where both the deck and ceiling are retained it may be possible to show that insulation is not economically viable. The regulations define economically feasible as situations where the work of incorporating additional insulation (materials and labour) is repaid by the saving in fuel bills within 15 years. See Approved Document L1B for clarification.

What insulation do you need to provide?

Part L of the building regulations relates to the conservation of fuel and power. In most cases you will need to provide extra thermal insulation.

The standard you need to reach depends on the roof construction. For pitched roofs where insulation is at ceiling level the U-value would be 0.16W/m2K; for pitched roofs where insulation is between the rafters the U-value would be 0.18W/m2K; and for flat roofs the U-value would be 0.18W/m2K.

Generally to achieve the U-value for a pitched roof, (with the insulation at ceiling level and a conventional roof void), you will need at least 270mm of mineral fibre.

Flat roofs - consider providing a warm deck roof. With all the insulation on top of the decking - this will raise the height of the roof typically by 125mm. If you do not wish to follow this method the introduction of additional insulation will involve either lifting the roof deck or removing the ceiling. For alternative solutions guidance should be sought from the manufacturer of the insulation you wish to use. In addition there is also guidance in Table A1 of Approved Document L1B.

In all cases, other than for warm deck solutions and lead roofs, you must consider how the prevention of condensation in roof spaces is to be addressed. This may be by using a breathable membrane for a pitched roof, installed in accordance with the manufacturers recommendations (including a vapour control layer at ceiling level), or providing roof ventilation as recommended in Approved Document C of the Building Regulations, typically in the form of soffit and ridge ventilation.

Other Building Regulations you need to be aware of

A2 - Loading - on many like for like replacements the roof structure has stood the test of time, (so it will not need strengthening), but expect to add additional purlins and struts where the structure is poor and rafters have deflected over time.

B4 - Fire Resistance - the new roof coverings need to achieve at least an AC fire rating. This is particularly important for flat roofs, which will require either 12.5mm spar chippings bonded to the felt or a specialist roof covering that achieves the rating.

C2 - Resistance To Moisture - New materials must be suitable for the pitch and fitted in accordance with manufacturer's instructions.

Building Regulation approval

Before recovering a roof that requires Building Regulation approval you must submit a Building Notice at least 48 hours prior to commencing the work on site, which must be accompanied by the fee charged by your local authority building control office. Works to buildings other than dwellings may require the submission of a Full Plans application, rather than a Building Notice, depending on the complexity of the work.

If you are in any doubt on what solution you should adopt do not hesitate to contact your local authority building control office before submitting your Building Notice or Full Plans application and they will be pleased to help you.

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